If you haven't received your flu vaccine, get to your doctor or pharmacist pronto. The Centers for Disease Control (CDC) and the American Academy of Pediatrics (AAP) recommend immunization for every person 6 months and older. Failure to do so may leave you sick with a fever causing weakness, dehydration, and/or an inability to work or attend school for a week or more.

This season, seven different types of flu vaccines are available including the traditional trivalent intramuscular injection that protects against three flu strains. For the first time, a quadrivalent vaccine, which protects against four strains of the flu virus,  is available both as a nasal spray and injection. 

We have answers to 12 frequently asked questions regarding influenza:

1. What Type of Flu Shot Is Right for Me?

Your healthcare provider will consider several factors before selecting which flu vaccine to administer.

Healthy children and adults 2-49 who don't have certain medical conditions that predispose them to flu-related complications can receive this season's quadrivalent vaccine as a nasal spray. There are also high-dose flu shots for people over 65 as well as vaccines for young children. Children between the ages of 6 months and 8 years may need two flu shots to give them full protection. This flu vaccine can be administered along with other childhood immunizations.

Having conditions such as asthma, diabetes, chronic lung disease, kidney, liver, endocrine or blood disorders, weakened immune systems or heart disease can mean you are more susceptible to the flu. Children younger than 5 (especially those under 2), people 65 or older, and pregnant women are more likely to develop complications from the flu, including pneumonia, and sinus and ear infections.

2. Who Should NOT Receive the Flu Vaccine?

Anyone who has ever had a severe reaction to a past flu vaccine should not be immunized. Reactions include a life-threatening allergic reaction that caused serious breathing difficulties (anaphylaxis) or Guillian-Barre syndrome (GBS), a rare—and usually temporary—disorder in which the immune system damages nerve cells, causing muscle weakness and sometimes paralysis. GBS is more common among older adults.

3. What Is the Difference Between the Nasal Spray Vaccine and the Flu Shot?

The nasal spray is a live, attenuated (weakened) virus. One hundred percent of this season's nasal spray (also known as FluMist®) vaccine supply is quadrivalent. It protects against two strains of influenza A (H1N1 and H3N2) and two strains of influenza B. It is only available for people ages 2 to 49 who are not in a high-risk group.

The traditional trivalent flu shot protects against the same two strains of influenza A and one strain of influenza B, and is produced with killed (inactive) viruses. There is also a quadrivalent flu shot available, which protects against the same four strains as the nasal spray. "The American Academy of Pediatrics does not recommend one vaccine over another this year," says Henry Bernstein, DO, MHCM, FAAP, associate editor of the AAP's Red Book Online (a periodically updated infectious disease report), and professor of pediatrics of Hofstra North Shore-LIJ School of Medicine. "Just be sure to get one."

4. When Should I Be Immunized?

The CDC and the AAP recommend being vaccinated as soon as the vaccine is available, which in many areas is late summer. It's important to note that protection against the flu isn't immediate: It takes the body about two weeks after vaccination to produce the antibodies that provide protection against the flu, which is why it's better to be vaccinated in October, before the height of the flu season.

Bernstein explains that receiving a vaccine after that—in December, for instance—is NOT too late. "It's a myth that receiving a vaccine after the fall months makes it less effective," he says explaining that influenza A could be a problem in November and influenza B might not appear until later in the winter. "Vaccine coverage lasts the entire flu season—six to eight months."

5. Is Being Vaccinated at a Doctor's Office Preferable to the Local Pharmacy?

It's not surprising for a pharmacist to be biased toward a drug store clinic and for a doctor to advocate being vaccinated in a medical office. If properly trained, Bernstein says pharmacists and nurse practitioners are well qualified to provide the vaccine. However, he worries about accurate information transfer—especially where the youngest patients are concerned: "If you take advantage of the convenience offered through a drug store clinic, be sure to inform your medical home about the vaccine you received. In other words, don't expect the pharmacy to follow up with your pediatrician."

Garth Ashbeck, MD, a family practice doctor with Maryland Primary Care Physicians in Arnold, MD, agrees: "For young children (6 months through 8 years) needing a double dose, it's important that the vaccines be administered four weeks apart to give the most protection," he says. "So information that falls through the cracks could be a problem." A doctor's office may also be able to handle an emergency situation better, Ashbeck adds.

6. What Are the Risks of Getting a Flu Shot?

Serious side effects from the flu shot are extremely rare. According to the CDC the most common side effects are soreness, redness, tenderness, or swelling where the flu shot was given and nasal congestion or a runny nose after administration of the nasal spray. Other minor side effects include: low-grade fever, body aches, and headaches.

7. Can a Flu Shot Give me the Flu?

No, the flu vaccines do not cause flu illness. The live, attenuated (weakened) viruses found in the nasal spray stimulate an immune response in the nose—the site where the flu enters the body and the body's temperature is cooler. They cannot infect the lungs where body temperatures are warmer. On the other hand, the flu shot—made with killed viruses—stimulates antibody production in the blood. If a person becomes sick with the flu within the first two weeks of receiving the immunization, it is likely because the body hasn't yet built up enough immunity.

8. Is the Flu Shot Safe?

Extremely. Each year hundreds of millions of Americans receive immunizations safely and the seasonal flu vaccine is no exception. Both the CDC and the FDA closely monitor it using multiple safety systems.

9. What if I Am Allergic to Eggs?

If you are allergic to eggs, be sure to inform your doctor as you may be a candidate for a new trivalent vaccine, called Flubok, that is not produced in fertilized chicken eggs. It is only available for people ages 18 to 49. Another new egg-free vaccine, called Flucelvax®, is also available for people 18 years and older. These vaccines use recombinant DNA technology, which is new to flu vaccine production, but helps make vaccines that have been approved by the FDA to prevent other infectious diseases. In the event of a pandemic (like the swine flu in 2009), this new technology enables faster production of the vaccine, since it's not dependent on the egg supply.

A note about children and egg allergies: Unfortunately Flubok and Flucelvax® are not approved for children, but Bernstein explains that in most cases children with egg issues can receive the traditional flu vaccine. "The data we have suggests that a single, age-appropriate dose is well tolerated by all people who have egg allergies, but the AAP does not have data about administering the mist to egg allergic patients yet," says the expert. He adds that for the time being, children with egg sensitivities should get the injection.

10. I'm Pregnant. Should I Be Vaccinated?

Bernstein and Ashbeck emphasize that every pregnant woman should receive a vaccine while they are expecting and they can get it in any trimester. "Important antibodies are passed on to the fetus that protect the baby during the first six months of life," Bernstein says.

11. Can I Still Get the Flu if I've Been Immunized Against it?

Unfortunately, yes, says Bernstein, who explains that none of the vaccines offer complete protection. Nonetheless, some protection is better than none. Various strains of the flu circulate every year. Annual recommendations about which strains to include are the result of expert review of influenza disease surveillance from the previous flu season and laboratory data collected from all over the world. "Sometimes, there's a perfect match, and that's great, but viruses can mutate or drift and the strain that is circulating might be different or a mismatch to what's in the vaccine," the expert admits. "That may vary by region. Within the United States, for example, the east might have an outbreak in the fall and the west might have one in the winter. Or influenza B might be an issue in the south but influenza A is causing a problem in the midwest."

Even so, antibodies made in response to vaccination with one flu virus can sometimes provide protection against different but related viruses, according to the CDC.

12. Are Any Flu Vaccine Shortages Expected This Year?

No, says Bernstein, who adds that going forward, shortages will be less of an issue since additional vaccines can be manufactured more quickly thanks to recent technology that is faster and doesn't rely on fertilized chicken eggs—the method used to make flu vaccines for more than 50 years.

Henry Bernstein, DO, MHCM, FAAP, approved this article.



Henry Bernstein, DO, MHCM, FAAP, associate editor of the Red Book Online and professor of pediatrics of Hofstra North Shore-LIJ School of Medicine. Phone interview, 20 November 2013.

Garth A. Ashbeck, MD, primary care physician with Maryland Primary Care Physicians in Arnold, MD. Phone interview, 19 November 2013.

Goar Alvarez, PharmD, director of pharmacy services at Nova Southeastern University in Fort Lauderdale, FL. Phone interview, 18 November 2013.

Centers for Disease Control and Prevention. "Live Attenuated Influenza [LAIV] (The Nasal Spray Flu Vaccine." Web. Accessed 20 November 2013.